Is over sleeping bad for the brain and keeping fit etc.

Tough question: This is a difficult question and often is debated. If you are 12, it is generally acceptable to sleep a lot as the theory is that the brain is still developing and needing time to " rest" and develop synaspes and myelin. Finally, oversleeping is a relative term. You also want to make certain that there isn't some metabolic cause like hypoglycemia or hypothyroidism.